The factory of CPDC (TAIL) An-shun site, Tainan, Taiwan was involved in the alkali-chlorine industry in the early years. Since sludge and wastewater were inappropriately discharged, soil at the area of the factory was highly contaminated with dioxin and mercury at the same time, which is very difficult to be remedied.
The existing techniques which have been disclosed for treatment of this kind of highly contaminated soil include heat treatment, adsorption, bacterial degradation and organic solvent extraction methods. Among these, the heat treatment method employs thermal desorption to isolate the contaminants from the soil, and such a heat treatment technique has been described in TW 201408389. It is well known that a considerable amounts of dust will be generated during treatment of the soil, hence, in the process described in TW 201408389, it is easy to block the system by the contaminants since the heat treatment is performed directly, resulting in the problem of instability of the process.
In addition, since the heat treatment process for contaminated soil will generate dust in an amount of 2-3%, about 25% of PM 2.5 based on the total volume of the dust, and additional air pollution problems will be caused if the dust without further treatment spreads into the air.
In view of the foregoing, it is necessary to propose a highly stable recycling method and apparatus for treatment of soil contaminated with mercury and dioxin, in order to solve problems of the existing techniques.